Herbicidal 1,5-dithia-2,4,6,8-tetrazacyclooctane-3,7-dione

ABSTRACT

Novel 1,5-dithia-2,4,6,8-tetrazacyclooctane-3,7-diones, useful as herbicides, are prepared by cyclodimerizing an Nchlorothiourea compound in the presence of an organic nitrogen base having no free hydrogen atoms, e.g., a tertiary organic amine or a pyridine compound.

United States Patent Magee 1 Aug. 12, 1975 HERBICIDAL l,5-DlTl-llA-2,4,6,8-TETRAZACYCLOOC- TANE-3,7-DIONE [75] Inventor: Philip S. Magee, Ignacio, Calif.

[73] Assignee: Chevron Research Company, San

Francisco, Calif.

Filed: Sept. 30, 1974 App]. No: 510,272

Related U.S. Application Data [62] Division of Ser. No. 34!,005, March 14. 1973, Pat.

[52] U.S. Cl. 71/90 [51] Int. Cl. AOln 9/14 [58] Field of Search 71/90 5 7 ABSTRACT Novel 1,5-dithia-2,4,6,8-tetrazacyclooctane-3 ,7- diones, useful as herbicides, are prepared by cyclodimerizing an N-chlorothiourea compound in the presence of an organic nitrogen base having no free hydrogen atoms, e.g., a tertiary organic amine or a pyridine compound.

12 Claims, N0 Drawings HERBICIDAL I l.5-DlTHIA-2.4.6,S-TETRAZACYCLOOCTANE-SJ- DIONE v, This is a division of application Scr. No. 341.005. filed Mar. 14. I973. now Pat. No. 3.853.853.

DESCRIPTION OF THE PRIOR ART French Patent 39.284. granted May 29. I972. discloses the reaction of urea compounds and sulfur dichloride to produce acyclic dimeric bis-urea sulfides. U.S. Ser. Nos. 250.895 of Cleveland and 25(l.9 ()7 of Kohn et al.. both filed May 5. I972. disclose the reaction of N-chlorothio urea compounds and sodium io dide to produce acyclic dimeric bis-urea disulfides.

SUMMARY OF THE INVENTION It has now been found that an N-chlorothio urea compound wherein the N'-nitrogen atom of the urea compound has at least one hydrogen substitucnt can be cyclodimerized in the presence of a tertiary organic nitrogen base. i.e.. an organic nitrogen base having no hydrogen substituted on the nitrogen atom. to produce a l.5-dithia-2.4.6.S-tetrazacyclooctane-3.7-dione compound.

DESCRIPTION OF THE INVENTION The N-Chlorothio Urea Reactant In general. any N-chlorothio urea compound having an N-chlorothio substituent on one urea nitrogen atom and a hydrogen substituent on the other urea nitrogen atom is suitably employed for preparing the l.5-dithia 2.4.6.X-tetrazacyclooctane-3,7-dione compounds of the invention. A class of suitable N-chlorothio urea rcactants may be represented by the following formula (I) wherein R and R individually are hydrogen. lower alkyl of l to 6 carbon atoms. cycloalkyl of to 8 carbon atoms. hydrocarbyl aryl off: to 10 carbon atoms or aryl of 6 to 10 carbon atoms substituted with l to 4 fluorine, chlorine. bromine. trichloromethyl. trifluoromethyl. alkoxy of l to 4 carbon atoms or nitro groups.

Representative alkyl groups which R and R may represent include methyl. ethyl. n-propyl. ispropyl. nbutyl. t-butyl. n-pentyl and n-hexyl. The preferred alkyl group is methyl.

Z-chloro--l-mcthylphcnyl. Z-tluoro-4-methylphenyl. 4- chlorobenzyl. 4-fluorobcnzyl. Z-(Z-fluorophenyl )ethyl'; alkoxysubstituted aryl groups such as methoxyphenyl. I 4 ethoxyphenyl. 4-mcthoxy-2- methylphenyl. 4-mcthoxybenzyl; nitro-substituted aryl groups such as Z -nitrophenyl. 4-nitrophcnyl and 4- nitrobenzyl; and aryl groups substituted with different substituents such as 2-methoxy-4-chlorophenyl and 2 chloro-4-nitrophenyl. Substituted aryl groups preferably have I to 2 substituents. Preferred substituted aryl groups are halo-substituted phenyls. especially those having I to 2 fluorine or chlorine substituents.

Preferably R is alkyl of l to 2 carbon atoms. especially methyl.

Preferably R is phenyl or phenyl substituted with l to 2 halogens of atomic number 9 to 35 (fluorine or chlorine). trifluoromethyl groups, nitro groups. alkyl of l to 2 carbon atoms. or alkoxy of l to 2 carbon atoms.

The N-chlorothio ureas are prepared by sulfenylation of a urea compound in accordance with the following equation I):

l H H SCI H (II) '(I) wherein R and R have the same significance as previously defined and B is an acid acceptor. v

The acid acceptor is an organic base such as a pyridine compound or a trialkylamine compound. Suitable pyridine compounds are pyridine and pyridine com pounds of 6 to 10 carbon atoms and of -l to 2 alkyl groups such as 2-methylpyridine. Z-ethylpyridine. 3- methylpyridine. 3.5-dimcthylpyridinc. and 2- butylpyridine. Suitable trialkylamines are those wherein the alkyl group contains individually l to 4 carbon atoms. such as trimethylamine. triethylamine. tripropylamine and tributylamine.

Generally. sulfur dichloride of reasonable purity. e.g.. greater than 98% purity. is employed. The sulfur dichloride preferably contains small amounts of an inhibitor such as tributylphosphate or triethylphosphate and is freshly distilled before use.

The sulfur dichloride and the urea compound (II) are employed in substantially equimolar amounts. e.g.. the molar ratio of sulfur dichlorideto the urea compound (II) generally varies from about l.5:l to l:l.5. although molar ratios of sulfur dichloride to the urea compound of l'.2:l to l:l are preferred. The molar ratio of acid acceptor to sulfur dichloride is also substantially equimolar. e.g..'the molar ratio of acid acceptor to sulfur dichloride varies from about l.2:l to l:l.2. although molar ratios of acid acceptor to sulfur dichloride of 1:] to l:l.2 are preferred.

In general. the reaction is accomplished by reacting the urea (II) and the sulfur dichloride in the presence of the acid acceptor compound in an inert diluent. The reaction is suitably conducted by adding the sulfur dichloride to a mixture of the urea and the acid acceptor in an inert diluent. Alternatively. the reaction is conducted by adding a mixture ofthc urea and acid acceptor to a solution of the sulfur dichloride in an inert diluent. However. the preferred method for conducting the reaction comprises reacting the urea and sulfur dichloride in the presence of a limited amount of free. uncomplcxed acid acceptor. This is suitably accomplished by the addition of the acid acceptor to a substantially equimolar mixture of the urea and the sulfur dichloride so that the mols of free acid acceptor to the total mols of urea reactant and N-chlorothio urea product is less than 0.2: l preferably less thanl). l l and more preferably less than 0.05:1. In other words. during the course of the reaction between the sulfur dichloride and the urea reactant, there should be at least 5 mols of the urea reactant and the N-chlorothio urea product per mol of acid acceptor which is not complexed with hydrochloric acid. Provided that the reaction is conducted with the restricted amount of acid acceptor indicated above. the contacting of the acid acceptor with the mixture of the urea and the sulfur dichloride can be conducted by a variety of procedures. In one modification. the acid acceptor is added in increments. e.g., dropwise. in an inert diluent; if desired. to a mixture of the urea and sulfur dichloride in an inert diluent. In another modification. the acid acceptor is added continuously to a mixture of the urea and sulfur dichloride in an inert diluent.

Suitable inert diluents for the reaction include alkanes of 5 to l() carbon atoms. such as hexane. isooctane and decanc; aromatic compounds such as benzene and chlorobenzene; oxygenated hydrocarbons such as acyclic alkyl ethers. c.g.. dimcthoxyethane and dibutyl ether; and cycloalkyl ethers, c.g.. dioxanc. tetrahydrofuran and tetrahydropyran. Other suitable diluents include nitriles such as acetonitrile and propionitrile.

Preferred diluents are chlorinated hydrocarbons of l to 2 carbon atoms, such as methylene dichloride. chloroform. carbon tetrachloride and ethylene dichloride. Generally. the amount of diluent employed ranges from 1 to 5() mols per mol of sulfur dichloride.

The reaction is suitably conducted at a temperature between 20C. and the boiling point of the diluent. although temperatures between 0C. and 50C. are preferred. The reaction is conducted at or above atmospheric pressure.

The N-chlorothio urea may be isolated by conventional procedures. c.g.. filtration, extraction. distillation. chromatography. etc. However. it is generally preferrcd to filter the hydrochloride salt of the organic base formed during the reaction and to employ. without further purification, the resulting solution of the N- chlorothio urea in the inert diluent in the preparation of the l.5dithia-2.4.6.8 tetrazacyclooctane3.7-dione compounds of the invention.

It is appreciated, of course.that the Nchlorothio urea (l) is formed by the substitution of a hydrogen (I) II\') substituent on a urea nitrogen atom by a sulfenyl chlo ride group. Since the urea (II) has more than one hydrogen substituted on a urea nitrogen. a mixture of monochlorothio derivatives is therefore generally formed [unless the urea (II) is symmetrical. i.e.. R is wherein R and R have the same significance as defined above and B is an organic nitrogen base as defined below.

As depicted in equation 2), the reaction of a single N-chlorothio urea reactant with the organic nitrogen base produces a single symmetrical l.5-dithia-2.4.6,8- tctrazocyelooctane-3.7-dione product. By way of illusl. the reaction of N-chlorothio urea and an organic nitrogen base, c.g.. pyridine. produces l.5-dithia- 2 4 6.8-tetrazacycl mctane-3.7-dione;

2. the reaction of N-chlorothio-N-mcthyl urea and an organic nitrogen base produces l.5-dithia-2 6- dimethyl-2.4.6.8-tctrazacyclooctane-3.7-dione; and

3. the reaction of N-chlorothio-N'-phenyl urea and an organic nitrogen base produces l.5-dithia-2.6- diphenyl-2.4.6.8-tetrazacyclooctane-3.7-dione.

The reaction depicted in equation (2) may also be conducted with two different N-chlorothio urea reactants. As depicted below in equation (3 the use of two different N-chlorothio ureas generally produces a random mixture of l.5-dithia-2.4.6.S-tetrazacyclooctane- 3.7-dio nc products.

wherein R R and B are as defined above and R and R individually represent the same groups as R and R By way of illustration. the reaction of N-chlorothio-N- methyl-N'-phenyl urea and N-chlorothio-N-naphthyl urea according to equation (3) produces a mixture of 1.5-dithia-2,b-dimethyl-4.8-diphenyl-2.4.-6,8- tetrazacyclooctane-3,7-dione; l,5-dithia-2.6- dinaphthyl-2.4,6,8-tetrazacyclooctane-3,7-dione: and l,5-dithia-Z-mcthyl4-phenyl-b-naphthyl-Z.4.6.8- tetra2cyclooctane-3,7-dione.

The tertiary organic nitrogen base employed in reactions (2) and (3) are those having no hydrogen atoms on the nitrogen atom. i.e.. no N-H groups. Such organic nitrogen bases include trialkylamines wherein the alkyl groups have 1 to carbon atoms, wherein two alkyl groups may be joined to form a 5- to b-membered heterocyclic ring with the nitrogen atom. such as trimethylamine, triethylamine. tripropylamine. trihexylamine, N-methylpyrrolidine and N-methylpiperidine, and pyridine compounds of 6 to 10 carbon atoms, such as pyridine, lutidines, collidines. and 2-butylpyridine. The preferred organic nitrogen bases are pyridine compounds.

The N-chlorothio urea reactant (l) and the organic nitrogen base are generally employed in substantially equimolar amounts. e.g.. the molar ratio of N- ehlorothio urea to base generally varies from about 1.5:1 to l l .5. Preferably, however, at least one mol of base is employed per mol of N-chlorothio urea. i.e., the molar ratio of N-chlorothio urea to base is preferably 1:1 to 1:15.

The reaction between the N-chlorothio urea and the base is conducted in an inert diluent, e.g.. the same diluent employed in the preparation of the N-chlorothio urea. Generally, the amount of diluent employed ranges from 1 to 50 mols per mol of N-chlorothio urea. The reaction is suitably conducted at a temperature between C. and the boiling point of the diluent, although temperatures between 0C. and 75C. are preferred. The reaction is conducted at. below or above atmospheric pressure. For convenience, the reaction pressure is generally atmospheric. The 1.5-dithia- 2.4.6,8-tetrazacyclooctanc-3,7-dione product is isolated and purified by conventional procedures such as filtration, extraction. chromatography, or crystallization.

The preparation of representative compounds of the invention are illustrated by the following examples.

EXAMPLES Example 1 Preparation of N-chlorothio-N-methyl-N'-2-fiuorophenyl urea A 5.7 g (0.055 mol) sample of sulfur dichloride was added dropwise to a mixture of 8.4 g (0.05 mol) N- methyl-N-2-fluorophenylurea and 4.7 g (0.06 mol) pyridine in 50 ml methylene chloride cooled in an ice bath. After the completion of the addition. the pyridine hydrochloride formed during the reaction was filtered. Hexane was added to the filtrate to precipitate some additional pyridine hydrochloride. which was removed by filtration. Evaporation of the resulting filtrate gave a clear. red oil. The nuclear magnetic resonance spectrum of the oil showed an N-methyl singlet at 3.5 ppm (relative to tetramethylsilane). Elemental analysis showed:

Cale. Found 7: S l3.b l3.h /l (.l l5.l l5.4

Example 2 Preparation of N-chlorothioN-methyl-N'-3,4-dichlorophcnyl urea Example 3 Preparation of N-chloro'thio-NN-dimethyl urea Pyridine. 9.48 g (0.12 mol) was added dropwise to a solution of 8.8 g (0.1 "mol) N,N-dimethyl urea and 1 1.3 g (0.1 1 mol) sulfur dichloride at 2530C. Pyridine hydrochloride was then filtered from the reaction mixture to give a solution of the N-chlorothio urea product in methylene chloride. The nuclear magnetic resonance spectrum of the product showed a singlet at 3.5 ppm for the Nmethyl group and a doublet at 2.95 ppm for the l\l-methyl group.

Example 4 Preparation of l ,5-dithia-2,6-di( 2-fluorophenyl 4.8-dimethyl-2,4.6,8-tetrazacyclooctane-3.7-dione A 0.15-mol sample of N-chlorothio-N-methyl-N'-2- fluorophenyl urea in ml methylene dichloride and 12 g (0.15 mol) pyridine was mixed at about 25C. and warmed to 45C. during a 15-minute period. The reaction mixture was filtered to remove the pyridine hydrochloride salt formed during the reaction. The filtrate was evaporated under reduced pressure to give sticky, solid residue. The residue was treated with water, filtered, and dried to give 4.8 g of product as a white solid, mp. l83186C. Elemental analysis for C,,H,, F l l.,()- ,S showed:

Cale. Found /1 F 9.95 10.32 /1 Q l6.l2 I622 Example 5 Preparation of l,5-dithia-2.6-di( 4-chlorophenyl 4,8-dimethyl-2,4.6.8-tetrazacyclooctane-3.7-dione A mixture of 15 g (0.081 mol) N-methyl-N-4- chlorophenyl urea, 8.5 g (0.083 mol) freshly distilled sulfur dichloride containing minor amounts of triethylphosphate and 6.7 g (0.083 mol) pyridine in 150 ml methylene dichloride was stirred at about 25C. for 1 hour. To precipitate the pyridine hydrochloride salt formed during the reaction, the volume of the reaction mixture was reduced about one-third by evaporation under reduced pressure. The reaction mixture was then 7 filtered to give a solution of N-ChlOl'OthltFNdTlLllh}l N'-4-chlorophenyl urea. I

A 6.7-g (0.83 mol) sample of pyridine was added to the above N-chlorothio urea solution. The mixture was stirred at about 25C. for 1 hour and then at ab ut I 40C. for onehalf hour. The mixture was allowed to stand for about 2 days and then filtered. The filtrate was evaporated under reduced pressure to give the crude product. The residue of pyridine hydrochloride salt was treated with water. filtered and dried to give an additional sample of crude product. Recrystallization of the combined crude product from chloroform gave the product as a pale yellow solid. dec. 196C. Osmometer molecular weight determination gave a value of 421 (calculated 429.35). Infrared analysis showed carbonyl absorption at 6,1]. and no N-H absorption. Elemental analysis for C H Cl N O S showed:

Calc. Found Example 6 Preparation of l.5-dithia-2.6-di( m-trifluoromethylphenyl 4.8-dimethyl-2.4.6.8-tetrazacyclooctane-3.7-dione A mixture of g (0.069 mol) N-methyl-N'-m-trifluoromethylphenyl urea. 8.1 g (0.079 mol) freshly distilled sulfur dichloride containing a minor amount of triethylphosphate and 6.3 (0.079 mol) pyridine in 100 ml methylene dichloride was stirred for 1.5 hours at about C. A precipitate of pyridine hydrochloride salt was formed. The mixture was filtered and the filtered salt was washed with methylene dichloride.

To the methylene dichloride solution N-chlorothio-N-methyl-N'-m-trifluoromcthylphcnyl urea. prepared above. was for one-half hour. and then at about 40C. for one-half hour. The solution was allowed to stand at about 25C. for about 16 hours and filtered to remove the precipitated pyridine hydrochloride salt. The filtrate was concentrated and treated with hexane to precipitate additional salt. The additional saltwas filtered. and the filtrate was evaporated. The residue was slurried with water and then with methanol to give the product as a white solid. m.p. 153156C. Elemental analysis for C H,.;F.;N O S showed:

Calc. Found '71 1- 22.9 25.3 S 12.8 14.2

Example 7 Preparation of l.5-dithia-2.6-di( 2.5-dichlorophenyl 4.8-dimethyl-2.4.6.8-tetrazacyclooctane-3.7-dione A mixture of 15 g (0.0685 mol) N-methyl-N-2.5- dichlorophenyl urea. 8.1 g (0.079 mol) freshly distilled sulfur dichloride containing a minor amount oftriethyl- 8 hydrochloride salt formed during the reaction. The salt was removed by filtration and the filtrate was concentrated to give a solid precipitate. The solid precipitate was recovered by filtration. washed with water and dried to give the product as a yellow solid. dec. 220C. Elemental analysis for C H Cl ,N O S showed:

Cale. Found Example 8 Preparation of l.5-dithia-2,o-dicyclooctyl-4.X-dimethyl- 2.4.6.8-tetracyclooctane-3.7-dione A mixture of 18.3 (0.1 mol) N-methyl-N-cyclooctyl urea. 12 g (0.1 17 mol) freshly distilled sulfur dichloride containing a minor amount of triethylphosphate and 9.2 g pyridine was stirred at 25C. for 1 hour. The mixture was filtered to give a solution of N-chlorothio-N- methyl-N'-cyelooctyl urea. To the N-chlorothio urea solution was added 9.2 g pyridine The resulting reaction mixture was stirred at 25C. for one-half hour and then at 4045C. for one-half hour. The reaction mix ture was filtered and the filtrate was concentrated to precipitate the crude product. The crude product was washed with water. dried and recrystallized from hexane to give the product as a yellow solid. m.p.

87-90C. Elemental analysis for C. ..,H ;N ,O- ,S showed:

Calc. Found 74 56.6 58.2 J? H 8.5 9.0 '/l N 13.1 I34 s 14.9 12.:

Example 9 Preparation of l.5-dithia-2.6-di( 3.4-dichlorophenyl 4.8-dimcthyl-246.8-tetrazacycltmctanc-3.7-dione A 10.2 g (0.1 mol) sample of freshly distilled sulfur dichloride containing a minor amount of triethylphosphatc was added dropwise to a mixture of 21 g (0.1 mol) N-methyl-N-3.4-dichlorophenyl urea and 15 g (0.2 mol) pyridine. The reaction was exothermic. The mixture was stirred until the reaction temperature dropped to about 25C. The mixture was then warmed to C. and stirred for one-half hour. The pyridine hydrochloride salt formed during the reaction was filtered. The filtrate was evaporated under reduced pressure to give a semi-solid. The semi-solid was diluted with methylene dichloride and filtered to give the prod- -uct as a fine. white solid. m.p. l82l96C. Elemental ale. Found ,5 S 12.8 13.4 '7: Cl Y 25.4 28.4

The filtrate was evaporated to give a semi-solid residue. The residue was dissolved in methylene dichloride. washed with water. dried over magnesium sulfate. filtered andevaporated. The resulting residue was crystallized from ether to give yellow crystals of bis-( 1- mcthyl-3-l 3.4-dichlorophenyl ll -ureido) sulfide. m.p. l fil -166C.

The compounds of the present invention areaingeneral. herbicidal in both preandpost-emergenceappli- Preand post-emergence herbicidal tests on representative compounds of the invention were made using the following methods. Pre-Emergence Test cations. For pre-emergence control of undesirable veg- 5 A uceumc l i f rh tcgt compound wusvpro. etation. the herbicidal compounds will be applied in pared by mixing 750 mg of the compound. 220 mg of hcrhlcldillly effective dmmmm m the w m t or a nonionic surfactant and 25 ml of acetone. This solugmwth media lhc Vcgctlltlmh lllfcstcd with tion was added to approximately 125 ml of water conseeds and/or seedlings of such vegetation. Such applir i ing 156 mg of surfactant. cation will inhibit the growth of or kill the seeds. germis d f h tcst vegetation were l d i a pm f ating seeds and seedlings. For post-emergence appli- 'soil and the urea solution was sprayed uniformly onto cations. the herbicidal compounds will be applied dih il surfucc at d dos/3 f 33 Th pot was rectly to the foliage and other plant parts. Generally. tere d and placed in a greenhouse. The pot was watered the herbicidal compounds of the invention are effective intermittently and was observed for seedling emeragainst weed grasses as well as broadleaf weeds. Some l5 gcnee. health of emerging seedlings. etc.. for a 3-week may be selective with respect to the type of application period. Atthe end of this period the herbicidal effecand/or type of weed. tiveness of the compound was rated based on the physi- The compounds of the present invention can be used ological observations. A ()-to-l()() scale was used. 0 repalone as herbicides. However. it is generally desirable resenting'no phytoxicity. 100 representing complete to apply the compounds in herbicidal compositions kill; comprising one or more of the herbicidal compounds Post-Emergence Test intimately admixed with a biologically inert carrier. The test compound was formulated in the same man- The carrier may be a liquid diluent or a solid. 0%. in ner as described above for the pre-emergence test. The the form of dust powder or granules. In the herbicidal concentration of the test compound in this formulation composition. the active herbicidal compounds can he 35 was 5000 ppm. This formulation was uniformly sprayed from about ().()l to 95% by weight of the entirecompoon 2 similar pots of 24-day-old plants (approximately sition. l5 to 25 plants per pot) at a dose of 33 p./cm After Suitable liquid diluent carriers include water and orh l m h d d i d th werc l d in a greenhou e ganie solvents. c.g.. hydrocarbons such as benzene. toland then watered intermittently at their bases. as uene. kerosene. diesel Oil. fuel oil. and petroleum naphneeded, The plants were observed periodically for phytha. Suitable solid carriers are natural clays such as katotoxic effects and physiological and morphological reolinite. atalpulgite. and montmorillonite. In addition. sponscs to the treatment. After 3 weeks. the herbicidal talcs. pyrophillite. diatomaceous silica. synthetic fine effe tiveness of the compound was rated based on silicas. calcium aluminosilicatc and tricalcium phosthese b ti A 04 -100 Scale was d reprc phate are suitable carriers. Organic materials such as 35 senting no phytotoxicity and l()() representing comwalnut-shell flour. cottonseed hulls. wheat flour. wood l t kill, flour. or redwood-bark flour may also be used as a solid Th e lt of the te t a ear in Table I, in the Tacarrier. ble. the following abbreviations are employed:

The herbicidal composition will also usually contain 1 O wild (A f m a minor amount of surface-active agent. Such surface W Watergrass (Ecllilmclzlou c'rusgulli) agents are those commonly known as wetting agents. C Crabgrass (Digituriu .s'miguinulis) dispersing agents and emulsifying agents. and can be M Mustard (Brass/cu urvensis) anionic. cationic or non-ionic in character. The herbi- P Pigweed (Amurum/ms retroflarus) cidal compositions may also contain other pesticides. L Lamhsquarter (Clu'lmpmlium album) TABLE I Herbicidal Effectiveness Pre/Post Compound 0 W C M P 1.

Example 4 100 100 00 100 55 100/100 100 100 adjuvants. stabilizers. conditioners. fillers, and the like.

The amount of herbicidal compound or composition administered will vary with the particular plant part or plant growth medium which is to be contacted. the general location of application i.e.. sheltered areas such as greenhouses. as compared to exposed areas such as lileds as well as the desired type of control. Generally. for both preand post-emergent control. the herbicidal compounds of the invention are applied at rates of 2 to (10 kg/ha.. and the preferred rate is in the range of 5 to 40 kg/ha.

What is claimed is: I. An herbicidal composition comprising an herbicidally effective amount of a compound of the formula wherein R. R R and R individually are hydrogen. lower alkyl of l to 6 carbon atoms. cycloalkyl of 5 to 8 carbon atoms. phenyl. naphthyl. alkaryl of 7 to l() carbon atoms or aralkyl of 7 to l() carbon atoms. each of said phenyl, naphthyl. alkaryl or aralkyl groups being unsubstituted or substituted with from I to 4 substituents selected from the group consisting of fluorine. chlorine. bromine, trichloromethyl. trifluoromethyl. alkoxy of l to 4 carbon atoms or nitro. and a biologically inert carrier.

2. The composition ofclaim 1 wherein R. R". R and R individually are lower alkyl or phenyl substituted with a trifluoromethyl group or I to 2 fluorine. chlorine or bromine atoms.

3. The composition of claim 1 wherein R and R are lower alkyl and R and R are phenyl substituted with l to 2 fluorine or chlorine atoms.

4. The composition of claim 3 wherein R and R" are the same and R and R are the same.

5. The composition of claim 1 wherein the compound is l .5-dithia-2.6-di( Z-fluorophenyl )4.8-dimethyl- 2.4.6.8-tetrazacyclooctane-3.7-dione.

6. A method for controlling undesirable vegetation which comprises applying thereto an herbieidally effective amount of a compound of the formula chlorine. bromine. trichloromethyl. trifluoromethyl.

alkoxy of l to 4 carbon atoms or nitro.

7. The method of claim 6 wherein R, R R and R" individually are lower alkyl or phenyl substituted with a trifluoromethyl group or to 2 fluorine. chlorine or bromine atoms.

8. The method of claim 6 wherein R and R are lower alkyl and R and R are phenyl substituted with l to 2 fluorine or chlorine atoms.

9. The method of claim 8 wherein R and R. are the same and R and R are the same.

10. The method of claim 6 wherein the compound is l.5-dithia-2.6di( Z-fluorophenyl )-4.8-dimethyl- 2.4,6.8-tetrazacyclooctane-3.7-dione.

11. The method of claim 6 wherein the compound is applied pre-emergently.

12. The method of claim 6 wherein the compound is applied post-emergently. 

1. AN HERBICIDAL COMPOSITION COMPRISING AN HERBICIDALLY EFFECTIVE AMOUNT OF A COMPOUND OF THE FORMULA
 2. The composition of claim 1 wherein R1, R2, R3 and R4 individually are lower alkyl or phenyl substituted with a trifluoromethyl group or 1 to 2 fluorine, chlorine or bromine atoms.
 3. The composition of claim 1 wherein R1 and R4 are lower alkyl and R2 and R3 are phenyl substituted with 1 to 2 fluorine or chlorine atoms.
 4. The composition of claim 3 wherein R1 and R4 are the same and R2 and R3 are the same.
 5. The composition of claim 1 wherein the compound is 1,5-dithia-2,6-di(2-fluorophenyl)4,8-dimethyl-2,4,6,8-tetrazacyclooctane-3,7-dione.
 6. A method for controlling undesirable vegetation which comprises applying thereto an herbicidally effective amount of a compound of the formula
 7. The method of claim 6 wherein R1, R2, R3 and R4 individually are lower alkyl or phenyl substituted with a trifluoromethyl group or 1 to 2 fluorine, chlorine or bromine atoms.
 8. The method of claim 6 wherein R1 and R4 are lower alkyl and R2 and R3 are phenyl substituted with 1 to 2 fluorine or chlorine atoms.
 9. The method of claim 8 wherein R1 and R4 are the same and R2 and R3 are the same.
 10. The method of claim 6 wherein the compound is 1,5-dithia-2, 6-di(2-fluorophenyl)-4,8-dimethyl-2,4,6,8-tetrazacyclooctane-3,7-dione.
 11. The method of claim 6 wherein the compound is applied pre-emergently.
 12. The method of claim 6 wherein the compound is applied post-emergently. 